Cable grip



W. T. GLOOR CABLE GRIP March 2, 1965 3 Sheets-Sheet 1 Filed June 10,1963 ATTORNEYS W. T. GLOQR CABLE GRIP March 2, 1965 3 Sheets-Sheet 2Filed June 10, 1963 w. T. GLOOR 3,171,277

CABLE GRIP 3 Sheets-Sheet 3 March 2, 1965 Filed June 10, 1963 w MK v W LA \mi \N United States Patent Office 3,l7l,277 Patented Mar. 2, 19653,171,277 CABLE GRIP Wilbur T. Gloor, Berwyn, Pa., assignor, by mesneassignments, to The Warner & Swasey Company, Cleveland, Ohio, acorporation of Ohio Filed June 10, 1963, Ser. No. 286,680 3 Claims. (Cl.73103) The present invention relates to cable snubbing grips andespecially to cable snubbing grips for securing specimens of cablestested in tension.

A purpose of the invention is to eliminate the need for special endpreparation of cable tested in a tensile testing machine.

A further purpose is to eliminate the need for socketing the ends ofcable used in a testing machine.

A further purpose is to gradually reduce the tensile force in a cable asit passes around the grip so that the tensile force is minimal at a camlock.

A further purpose is to use the grips in pairs, one at each end of thecable.

A further purpose is to provide grips from which the cable can bereadily removed at the conclusion of the test.

A further purpose is to force a cantilever element toward an eccentriccam and increase the clamping force on the cable.

A further purpose is to utilize the drag of a cable through the cam lockto rotate the lock so that it increases its clamping force.

A further purpose is to fix each of two grips to a tension-load-applyingelement of a testing machine.

A further purpose is to allow the user to mount the grips in a testingmachine at a specific distance between the tangent points of the drums.

A further purpose is to permit an adjustment to set an initial load inthe specimen.

A further purpose is to provide a grip which works particularly well onstranded cable but can be used also on single wire like copper wire.

A further purpose is to provide a self energizing cam which tightensfurther as the cable pulls.

A further purpose is to deflect a cantilever lip to act against the camlike an anvil.

A further purpose is to position the axis of pull on the cable throughthe center of the cable.

Further purposes appear in the specification and in the claims.

In the drawings, I have chosen to illustrate two only of the numerousembodiments in which my invention may appear, selecting the forms shownfrom the standpoints of convenience in illustration, satisfactoryoperation and clear demonstration of the principles involved.

FIGURE 1 is a perspective view of a tensile testing machine utilizingthe cable grips of the invention to grip a cable test specimen.

FIGURE 2 is a front elevational view of the cable grip of the invention.

FIGURE 3 is a sectional elevational view taken on the line 3-3 of FIGURE2.

FIGURE 4 is a top plan view of the grip of FIGURE 2.

FIGURE 5 is a vertical section taken on the line 55 of FIGURE 3.

FIGURE 6 is a front elevational View of a modified form of theinvention.

FIGURE 7 is an elevational section taken on the line 7-7 of FIGURE 6.

FIGURE 8 is a fragmentary rear elevational View of some of thecomponents seen in FIGURES 6 and 7.

Describing in illustration but not in limitation and referring to thedrawings:

Tensile testing machines which apply a tensile load to a test specimento estabish a stress-strain relationship as well as a failure point arewell known wherein the load applied to the specimen is measured bysuitable gauging devices.

In using these testing machines, it is necessary to mount the specimento the load applying elements by a gripping device which does not allowthe specimen to slip. In the case of cable or wire rope specimens, ithas been conventional, for instance, to apply molten metal to the endstrands to enlarge the diameter. The enlarged end of the cable is thenseated in a socket formed in the force supplying element of the testingmachine.

Such socketing procedure is slow and expensive. By means of the presentinvention, the need to socket the cable test specimen is eliminated, andthe cable may be quickly and easily mounted in the testing machine. Thecable is merely wound around the outer circumference of a drum portionof a grip and then brought through an opening in the drum circumferenceto the inner circumference where it is engaged by an eccentric cam. Byvirtue of a cantilevered segment of the drum as well as the cam, thecable is securely held against slippage. T ension along the cableengaged with the grip is such that it is at a maximum at the tangentpoint where it first comes into contact with the grip drum and thengradually reduced to a minimum at the locked portion between thecantilever and the cam. The grip is so arranged that the greater thetension on the cable, the greater the grip exerted on the cable, so thatthere is no slippage between the grip and the cable.

Considering the test machine 10 as shown in FIGURE 1, a hydraulic orother suitable form of load applying cylinder 20 is fixed to a pressframe 21 having columns 22, a base 23, and a header 24. A suitablesource of pressure such as hydraulic fluid is fed to the cylinderthrough line 25 and the load imparted to the test specimen is measuredby any conventional testing machine 26. The grips consist of a lowergrip 27 and an upper grip 28.

The lower grip 27 is held by an adjustable bracket 30 having threadedcolumns 31 which support a header 32.

The grips 27 and 28 are identical, so that only grip 28 will bedescribed. The grip 28 consists of a drum holder 33 and a drum 35. Thedrum holder and drum are desirably integral but may permissibly be ofseparate sections fixed together by welding, bolting, or the like. Thedrum holder comprises a web 36 and a flange 37.

The flange 37 has a tapped hole at 38 which receives a threaded pistonrod 40 which is locked to the flange by a lock nut 41. The longitudinalaxis of the piston rod 40 is parallel to the longitudinal axis of thecable specimen being tested as later explained.

The flange 37 portion of the drum holder 33 has suitably an inner curvercontour or arcuate contour 41 extending at a constant radius from apoint 42 in the web 36.

The drum 35 comprises a rigid segment 43 and a cantilevered segment 45.The rigid segment 43 extends arcuately about the drum from a point 46 toa point 47 and is suitably integral with the web 36 throughout thisarcuate length. The cantilevered segment extends from point 46 to point48. A guide segment 50 extends arcuately from the rigid segment 43 at47.

Drum 35 has an inner circumference 51, an outer circumference 52, an endwall 53, and an end wall 54. The outer circumference has a groove havingsides 56 and 57 and a bottom 58. A slot 60 extends through the drum toseparate the cantilever segment 55 from the guide segment 50.

An eccentric cam having a shaft 66 and a clamping surface 67 isrotatably secured at its center of rotation 68 to the web 36 at 42. Thecam 65 is suitably held to the web by a shoulder screw 70 which has ashoulder 71 3 which bears against a counter sunk hole 72 in cam 65. Theshank of screw 70 has a threaded portion at 73 which engages a tappedhole 75 whose longitudinal axis coincides with point 42.

The inner circumference 51 is of constant radius with respect to point42 and the outer circumference 52 of the drum is of constant radius withrespect to the point 42. The surface 76 of clamp portion 67 iscylindrical in contour and of a knurled or roughened surface. A handle77 is positioned in cam 65 radially from the center of rotation 68 andis secured in the. shaft portion 66 at 78.

In operation, a test specimen 80, such as a cable, comprised of wirestrands, is laid in groove 55 of the drum and wrapped around the outercircumference of the drum a number of times, for example, two.

The radius of the outer circumference of the drum is such that when atensile force is brought to bear on the cable 80, the cable will extendfrom the drum in a tangent which is parallel to the longitudinal axis ofthe piston rod 40 which applies the tensile load to the grip.

After the cable is wrapped around the drum a suitable number of times,the end is brought over guide segment 50 which has a radius of curvature81 capable of imparting a gradual turn to the cable to direct it in atangent to the inner circumference of the cantilever segment at 82. Thecable is then laid on the inner circumference 51 of the drum between thecam 65 and the drum 35. The cam 65 has been rotated at this point toallow suflicient'clearance between the surface 76 and the innercircumference 51 to allow the cable to be readily put in place. The camis then rotated clockwise as viewed in FIGURE 2 until the clampingportion 67 of the eccentric cam 65 engages the cable 80 and holds ittightly against the cantilevered segment 45 of the drum 35 on the innercircumference 51.

The lower end of the test specimen 80 is similarly engaged in lowercable grip 27. It will be seen that the cable can extend to any lengthat 83 since it is not necessary to have a free end of the cable to mountthe cable in a grip. A load is then applied to pull the grips apart asby introducing fluid under pressure to cylinder 20 through feed line 25.As the specimen 80 is loaded, tension in the specimen tends to compressthe drum radially inward since the cable is wrapped around the drum. Theradial compression of the drum forces the cantilever portion 45 to bendfrom its anchor portion at 46 toward the cam, thus increasing theclamping force on the cable. At the same time, the drag of the cable 80through the eccentric cam and inner circumference of the cantileversegment tends to rotate the cam so that it increases its clamping force.This interaction of the cable 80, cantilever segment 45, and cam 65holds the cable 80 firmly. Tension in the cable is minimal at the camlock, and reaches a maximum in the free length of cable between thegrips, enhancing the probability of failure of the cable in its freelength. At the conclusion of the test, the cable is readily removed fromthe grips by rotating the cam 65 in a counterclockwise direction asviewed in FIGURE 1 by means of handle 77.

In an alternative embodiment as shown in FIGURES 6 and 7, I show a gripwhich provides adjustment of the drum 135 with respect to the drumholder 133. This allows the user to mount the grips in a testing machineat a specific distance between the tangent points of the drums, and thenapply an initial load to the specimen. For instance, it may be desirableto mount the grips in a testing machine at a specific distance of say 10inches between the tangent points of the drum and then preload the cableto an initial load of for example 10 pounds. By establishing identicalstarting characteristics on a plurality of specimens, the results can beaccurately compared.

In the description of this embodiment, common elements with theembodiment of FIGURES 1 to are given the same numbers with the prefix 1and will not'be further described.

In this embodiment, the drum is rotatable with respect to the drumholder 133. A web 135' is suitably integral with the anchored portion143 of the drum 135. The web 135 has a boss 144 which acts as a pivotwhich engages a hole 144 in the web 136 of the housing 133. The boss 144has a threaded extension 144 which receives a lock washer 144 and a locknut 144 A key having an arcuate surface 186 and a flange 187 passesthrough arcuate slot 188 in web 136. Flange 187 engages shoulder 189 ofrecess 190. Key 185 is held to the drum by suitable shoulder screws 191.An adjustable knob 192 having a head 193 and a threaded shaft 194- isthreaded into a tapped hole 195 in the cable drum holder 133. The end ofthe shaft at 196 engages the arcuate surface 186 of key 185 to suitablyrotate the key and drum counterclockwise as seen in FIGURE 6. A helicaltension spring 197 is anchored to the key at 198 and to the holder at199 to bias the drum in a clockwise direction as shown in FIGURE 6against the adjustable knob.

In operation, the modified cable grips of FIGURES 6 and 7 are placed inthe testing machine of, for instance, FIGURE 1 and the machine isadjusted so that the distance between the centers of rotation of thedrum and hence the distance between tangent points on the test specimenwill be a given distance. The adjusting knob 192 is then retracted toallow the drum 135 to rotate to a limiting position in a clockwisedirection as viewed in FIGURE 6. Preferably this distance will be 15degrees from a line parallel to the direction of force application tothe grip. The cable specimen is then loaded as described in the deviceof FIGURES 1 to 5. The adjusting knob 192 is then rotated to bearagainst the key 185 at surface 186 and rotate the drum in acounterclockwise direction about its pivot 144 so as to place the testspecimen under a tension load. The load imparted to the test specimencan be suitably determined by the indicator 26 on the testing machine.When the knob 192 has been rotated to impart a sutficient preload to thespecimen, the drum 135 is fixed in its final rotative position and thespecimen is now ready to be tested in the manner described in the deviceof FIGURES 1 to 5.

Desirably, the drum 135 is made to rotate through an arc ofapproximately 30 degrees with respect to the drum holder 133 as thisprovides suflicient travel to provide proper preload.

In view of my invention and disclosure, variations and modifications tomeet individual whim or particular need will doubtless become evident toothers skilled in the art, to obtain all or part of the benefits of myinvention without copying the structure shown, and I, therefore, claimall such insofar as they fall within the reasonable spirit and scope ofmy claims.

Having thus described my invention what I claim as new and desire tosecure by Letters Patent is:

1. In a gripping device for a cable: a drum holder having longitudinallyextending mounting means; a drum having an inner and an outercircumference and having a rigid segment rigidly connected to the drumholder and stationary relative thereto and a cantilevered segment; saiddrum adapted to receive a plurality of cable turns on its outercircumference; said rigid segment having a tangent extending from itsouter circumference in line with said longitudinally extending mountingmeans; said cantilevered segment extending in an arc and fixed at oneend of the arc to the rigid segment wherein the cantilevered segment canfiex radially with respect to the rigid segment under the force of acable wrapped on the drum outer circumference; and an eccentric campivoted on the drum holder and adapted to rotate into clampingengagement with the cable at the inner circumference of the drum at thecantilevered segment; wherein the gripped cable is wrapped around thedrum outer circumference and clamped between the cam and cantileveredsegment inner circumference whereby the cable extends from the grippingdevice in line with the said mounting means and tension on the cableflexes the cantilevered segment against the cam.

2. In a gripping device for a cable: a drum holder; a drum pivoted onthe drum holder, means for rotationally fixing the drum with respect tothe drum holder to impart an initial load to the cable including anadjusting knob having a head and a shaft, and a key on the drum incontact with the end of the shaft and adapted to be rotated by theadjusting knob; the drum having an inner and an outer circumference andhaving a rigid segment and a cantilevered segment; and an eccentric campivoted on the drum holder and adapted to rotate into clampingengagement with the cable at the inner circumference of the drum at thecantilevered segment, wherein the device receives References Cited bythe Examiner UNITED STATES PATENTS 1,282,643 10/ 18 Scott 241342,327,139 8/43 Scott.

2,372,962 4/45 Knochel et al 73103 X 3,000,068 9/61 Hughes 24134 RICHARDC. QUEISSER, Primary Examiner.

a cable wound around the outer circumference of the 15 DAVID SCHONBERG,Examiner.

1. IN A GRIPPING DEVICE FOR A CABLE: A DRUM HOLDER HAVING LONGITUDINALLYEXTENDING MOUNTING MEANS; A DRUM HAVING AN INNER AND AN OUTERCIRCUMFERENCE AND HAVING A RIGID SEGMENT RIGIDLY CONNECTED TO THE DRUMHOLDER AND STATIONARY RELATIVE THERETO AND A CANTILEVERED SEGMENT; SAIDDRUM ADAPTED TO RECEIVE A PLURALITY OF CABLE TURNS ON ITS OUTERCIRCUMFERENCE; SAID RIGID SEGMENT HAVING A TANGENT EXTENDING FROM ITSOUTER CIRCUMFERENCE IN LINE WITH SAID LONGITUDINALLY EXTENDING MOUNTINGMEANS; SAID CANTILEVERED SEGMENT EXTENDING IN AN ARC AND FIXED AT ONEEND OF THE ARC TO THE RIGID SEGMENT WHEREIN THE CANTILEVERED SEGMENT CANFLEX RADIALLY WITH RESPECT TO THE RIGID SEGMENT UNDER THE FORCE OF ACABLE WRAPPED ON THE DRUM OUTER CIRCUMFERENCE; AND AN ECCENTRIC CAMPIVOTED ON THE DRUM HOLDER AND ADAPTED TO ROTATE INTO CLAMPINGENGAGEMENT WITH THE CABLE AT THE INNER CIRCUMFERENCE OF THE DRUM AT THECANTILEVERED SEGMENT; WHEREIN THE GRIPPED CABLE IS WRAPPED AROUND THEDRUM OUTER CIRCUMFERENCE AND CLAMPED BETWEEN THE CAM AND CANTILEVEREDSEGMENT INNER CIRCUMFERENCE WHEREBY THE CABLE EXTENDS FROM THE GRIPPINGDEVICE IN LINE WITH SAID MOUNTING MEANS AND TENSION ON THE CABLE FLEXESTHE CANTILEVERED SEGMENT AGAINST THE CAM.